#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#define FROM   0.0
#define TO   100.0
#define STEP   0.01

#define sigmoid_slope -1.0

double INPUT=0.1;
double INITIAL_VALUE=10.0;
double INIT_SELFWGT=1.0;

typedef struct {
    double output;
    double thres;
    double state;
    double old_state;
    double inp_wgt;
    double self_wgt;
} neuron;


void initialize_neuron(neuron *a)
{
	a->output = INITIAL_VALUE;
	a->state = INITIAL_VALUE;
	a->thres = 0.0;
	a->inp_wgt = 1.0;
	a->self_wgt = INIT_SELFWGT;
}

double output_f(double value)
{
/*
	return 1.0 / ( 1.0 + exp(sigmoid_slope * value) );
	*/
	return value;
}

void update_neuron(neuron *a, double input)
{
	a->state += (- a->output 
				+ a->inp_wgt * input 
				+ a->old_state * a->self_wgt
				- a->thres) * STEP;
	a->output = output_f(a->state);
	a->old_state = a->output;
}

int main(int argc, char **argv)
{
	neuron a;
	double t;

	if ( argc != 4 ) {
		fprintf(stderr,"Usage: %s input initial self_wgt\n",argv[0]);
		exit( 0 );
	}
	INPUT=atof(argv[1]);
	INITIAL_VALUE=atof(argv[2]);
	INIT_SELFWGT=atof(argv[3]);

	fprintf(stderr,"INPUT=%f,INITIAL_VALUE=%f,INIT_SELFWGT=%f\n", 
		INPUT,INITIAL_VALUE,INIT_SELFWGT);
  initialize_neuron(&a);
	t = FROM;
	while ( t <= TO ){
		update_neuron(&a, INPUT);
		printf("%f %f\n", t, a.output);
		t += STEP;
	}
	return EXIT_SUCCESS;
}